I work at Google. I think it's half true.

I would not have passed the Google interview if I had not prepared. After 3 years, I have completely forgotten most of the prep. I couldn't even implement a binary search right now.

That said, I do have an innate ability for problem solving. I know another person, who has prepared significantly more than me (multiple months full-time) but still wasn't able to get an on-site interview. In my opinion, it requires at least a minimum level of intelligence, luck and preparation.